introduction of heterogeneous catalysis

低温等离子体在催化过程中的应用和机理研究

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Project Training Workshop – Catalyst Characterisation

Introduction of Heterogeneous Catalysis and Characterisations

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Shaojun xu

School of Chemistry, Cardiff University

UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Labs

Email: : [email protected]

Bioenergy – Carbon capture and utilisation – Energy Storage

EU RISE – BIOMASS-CCU

Marie Skłodowska-Curie Actions

Harwell Science and Innovation Campus

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UK Catalysis Hub

Diamond Light Source

Contents

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1. Introduction of Heterogeneous Catalysis

2. Kinetics of Heterogeneous Catalysis

3. Preparation of Heterogeneous catalysts

4. Characterisations of Catalysis





a phenomenon in which a small quantity of a substance (the catalyst) increases the rate of a chemical reaction without being consumed

What is Catalysis?

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Catalysis is a cycle of elementary steps

(at least three); catalytic sites are

regenerated

M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384


Reactants: gas / liquid phaseCatalyst: molecule

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Heterogeneous Catalysis?

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Reactants: gas / liquid phaseCatalyst: solid

The reaction inside the catalytic particle1. Transport of reactants (A, B, …) from the

fluid bulk to the catalyst surface2. Transport of reactants inside catalyst pores3. Adsorption or reactants to the catalytic site4. Surface reaction among molecules or

atoms adsorbed5. Desorption of products (R, S, . )6. Transport of products from pores to the

catalyst surface7. Transport of products from the catalyst

surface to the fluid bulk

Froment, G. F.; Bischoff, K. B.; De Wilde, J., Chemical reactor analysis and design. Wiley New York: 1990; Vol. 2.

Unsupported/supported catalystnanometer particles + support

Typical heterogeneous catalytic process

Why is the catalytic reaction faster?


Svante Arrhenius

1859 - 1927

Nobel Prize 1903

Energy barrier of the catalytic route much lower

Activation energy lowerReaction temperature lower

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Arrhenius Equation

How to translate the catalysis into kinetics?


Surface concentration of adsorbed species

↕Gas phase pressure

The adsorption isotherm: a curve of the amount of adsorbed molecules to the adsorbent surface as a function of the partial pressure or concentration of the adsorbate at a constant temperature.

Monolayer Multilayer

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Langmuir adsorption isotherm


Assumption:

➢ A fixed number of surface sites➢ Sites are either occupied or empty➢ All sites are equivalent➢ Adsorbates do not interact➢ Molecules and atoms adsorb on these sites

A: gas phase molecules,

S: vacant surface sites,SA: occupied surface sites,

Irving Langmuir 1881 - 1957

Nobel Prize 1932

An equilibrium constant, K:

Fraction occupied θA (0 < θ < 1)

𝐾 =𝜃

1 − 𝜃 𝑃

𝜃 =𝐾𝑃

1 + 𝐾𝑃9

Langmuir adsorption isotherm


𝐾 =𝜃

1 − 𝜃 𝑃𝜃 =

𝐾𝑃

1 + 𝐾𝑃

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At low concentration, adsorption is linearly proportional to P

At high concentration, it reaches a monolayer.

Larger value of K means

stronger binding, larger θ

K depend on T

Balance the catalyst-adsorbate interaction?


Paul Sabatier1854 - 1941

Nobel Prize 1912

The Sabatier Effect

optimum interaction

catalyst - adsorbate:

• not too strong

• not too weak A volcano plot for the decomposition of formic acid

using different transition metals as catalysts 11

Optimum coverage at right surface

Multilayer Adsorption and Condensation


The famous BET Isotherm first introduced in the 1930s by Brunauer, Emmett and Teller now considers also the possibility of multilayer adsorption and condensation as shown below.

Koduru, J. R, et al. In Rare-Earth Metal Recovery for Green Technologies, 2020; pp 87-109.

Saadi, R. et al. Korean J. Chem. Eng. 2015, 32 (5), 787-799. 12

M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384United States Patent Nos. 8,062,521 (“the ‘521 Patent”) and 9,101,863 (“the ‘863 Patent”)

Multiple length and time

scales

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Application of a Heterogeneous Catalyst

Natural: Clay/Zeoliters

Synthetic:

Crystalline aluminosilicatesMetal–organic frameworksMetal clusters/alloy

Bravo-

Suárez, J.

J.; et al,

ACS: 2013;

Vol. 1132, pp 3-68.

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Components of a Heterogeneous Catalyst Function:Chemical activityTypes:MetalsSemiconductor oxides and sulfidesInsulator oxides and sulfides

Function:High surface areaPorosityMechanical propertiesStabilityDual functionalActivityModification of active componentTypesOxides/Clays/Carbon

Function:On support:StructuralActivity inhinitiionActivity promotionOn active componentElectronicMorphologyPoisoning

Arsalanfar, M, etal, Journal of Industrial and Engineering Chemistry 2014, 20 (4), 1313-1323. 15


Preparation of a Heterogeneous Catalyst

Precipitation:To form non-soluble precipitate by desired reactions at certain pH and temperature

Adsorption & ion-exchange:Cationic: S-OH+ + C+ → SOC+ + H+

Anionic: S-OH- + A- → SA- + OH-

I-exch. S-Na+ + Ni 2+ ↔ S-Ni 2+ + Na+

Impregnation:Fill the pores of support with a metal salt solution of sufficient concentration to give the correct loading.

Dry mixingPhysically mixed, grind, and fired

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Lifecycle of Prepared Catalysts


Further treatment of prepared catalysts:Calcined to decompose the precursor and to receive desired thermal stability.

Commonly used Pre-treatmentsReduction: elemental metal is the active phaseSulphidation: a metal sulphide is the active phaseActivation: for the best performance.

Typical catalyst life span:Can be many years or a few mins.

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M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384 18


Variables in Catalytic Process

Known / Controllable Variables

Reactor system

Temperature Pressure

Catalyst system

Specific surface

area

Porosity

Surface roughness

Metal loading

Interaction

between

metal andsupport

Diagnostic system

In line

/

In situ

Multivariable Control DesignSingle Variable Control 19


Hyphenated Methods for Species Analysis

Sarker, S. D.; Nahar, L., Hyphenated Techniques and Their Applications in Natural Products Analysis. pp 301-340. 20


Sarker, S. D.; Nahar, L., Hyphenated Techniques and Their Applications in Natural Products Analysis. pp 301-340.

Information from Hyphenated Techniques

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Hyphenated Methods for Species Analysis

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Characterization for Heterogeneous Catalysts

A.Alshammari and V.N. Kalevaru. Catalytic Application of Nano-Gold Catalysts, Chapter 3, P65P. Lanzafame,; et al., Catalysis Science & Technology 2017, 7 (22), 5182-5194.

Operando characterisations(Simultaneous Reaction + Catalyst

diagnostics)

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Fundamental Research on Catalysts

A.Alshammari and V.N. Kalevaru. Catalytic Application of Nano-Gold Catalysts, Chapter 3, P65

The overall concept follows the deep characterisation of the catalytically active sites,

detailed kinetic analysis, determination of the rate determining step and based on this knowledge the targeted design of advanced catalysts for process optimisation.

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Dual functional catalytic materials of Ni over Ce-modified CaO

sorbents for integrated CO2 capture and conversion

Sun, H.; et al., Appl. Catal., B. 2019, 244, 63-75. 25

Diffuse reflectance infrared fouriertransform spectroscopy (DRIFTS)

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Project Training Workshop – Catalyst Characterisation

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Shaojun xu

School of Chemistry, Cardiff University

UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Labs

Email: : [email protected]




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introduction of heterogeneous catalysis

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